Vapor recovery

ABSTRACT

This disclosure relates to a vapor recovery system particularly adapted to recover volatile liquid vapors from a tank during the filling of a tank with the volatile liquid. The disclosure particularly relates to the operation of the vapor recovery system, particularly the absorber system thereof, at a low temperature whereby maximum efficiency can be obtained with low pressures. The absorber system is also improved by recirculating the absorbing liquid to minimize air absorption in the liquid stream. The collective liquid returning to the liquid reservoir is utilized as a heat exchange medium to improve the efficiency of other portions of the recovery system.

[ 1 Nov. 13, 1973 VAPOR RECOVERY Richard A. Nichols, Santa Ana, Calif.

[73] Assignee: Parker-Hannifin Corporation,

Cleveland, Ohio [22] Filed: Dec. 7, 1970 [21] Appl. No.: 95,640

[75] Inventor:

2,765,872 10/1956 Hartman et al 55/88 2,947,379 8/1960 Aubrey 220/85 VR3,266,262 8/1966 Moragne 62/54 Primary Examiner-Meyer Perlin AssistantExaminer-Ronald C. Capossela Att0rneyDiller, Brown, Ramik & Holt [57]ABSTRACT This disclosure relates to a vapor recovery system particularlyadapted to recover volatile liquid vapors from a tank during the fillingof a tankwith the volatile liquid. The disclosure particularly relatesto the operation of the vapor recovery system, particularly the absorbersystem thereof, at a low temperature whereby maximum efficiency can beobtained with low pressures. The absorber system is also improved byrecirculating the absorbing liquid to minimize air absorption in theliquid stream. The collective liquid returning to the liquid reservoiris utilized as a heat ex-' change medium to improve the efficiency ofother portions of the recovery system.

28 Claims, 3 Drawing Figures PATENTEUNUY 13 I975 SHEET 2 BF 2 \NVENTORVAPOR RECOVERY This invention relates in general to a vapor recoverysystem, and more particularly to a system for recovering volatile liquidvapors which result during the filling of a tank. The recovery system isparticularly adaptable to the recovery of vapors which occur during thefilling of fuel tanks.

BACKGROUND OF THE INVENTION When filling a tank with a highly volatileliquid, such as a hydrocarbon fuel, large quantities of vapor occur. Formany years, these vapors have been lost to the atmosphere with theresultant loss of the value of the vapors. In addition, the atmospherehas been polluted by such escaping vapors.

In the past, systems have been developed by others. A typical system isthat found in the patent to Albert H. Tompkins, Jr. entitled VaporRecovery System, US. Pat. No. 2,849,150, granted Aug. 26, 1958. Theseprior systems include, among other apparatus, an absorber wherein therecovered vapor is absorbed into the recovery liquid and is returned tothe liquid storage reservoir and sizeable quantities of absorbed air arealso released at the reservoir.

PURPOSE OF THIS INVENTION In accordance with this invention, it isproposed to provide a relatively simple vapor recovery system which isof sufficient efficiency so as to be economically feasible. in the firstplace, the absorbing liquid is recirculated through the absorber tominimize air absorption. This provides for a maximum over-all lowtemperature absorber efficiency.

It is also proposed to refrigerate the liquid within the absorber tankso that the absorber operates at a low temperature which allows theoperation of the absorber at lower pressures with the same or betterefficiency than before.

The vapor recovery system also utilizes the low temperature liquidstream returning to the liquid storage reservoir as a heat exchangemedium to lower the temperature of all liquid being separatelysuppliedto the absorber system whereby the efficiency of the low temperatureoperation of the absorber system is enhanced.

The liquid being returned to the liquid supply reservoir is passed intoa flash separator wherein air entrapped withinthe returning liquid byabsorption may be removed thereby further increasing the efficiency ofthe recovery system.

A further feature of the vapor recovery system is the passage ofcompressed incoming vapors first through a finned tube aftercooler andthen to a liquid aftercooler with the finned tube aftercooler initiallyreducing the temperature of the hot compressed vapors sufficiently toprevent vaporization of the liquid coolant within the liquidaftercooler. The use of the finned tube aftercooler also increases theliquid aftercooler efficiency allowing the same to be used at lower thannormal pressures. The use of the finned tube aftercooler further permitsan optimum use of temperature gradients in the two aftercoolers, therebygiving greater over-all efficiency.

With the above and other objects in view that will hereinafter appear,the nature of the invention will be more clearly understood by referenceto the following detailed description, the appended claims and theseveral views illustrated in the accompanying drawings:

IN THE DRAWINGS FIG. 1 is a diagrammatic flow diagram of an embodimentof the invention.

FIG. 2 is a diagrammatic flow diagram of a modified compressorarrangement for handling the recovered vapors.

FIG. 3 is a diagrammatic flow diagram of another embodiment of theinvention.

Referring now to the drawings in detail, in FIG. 1 there is illustrateda vapor recovery system which is identified by the numeral 5. Since thevapor recovery system 5 finds particular usage in the filling of fueltanks, particularly tanks of tank trucks, the system will be describedas applied thereto although it is to be understood that the invention isnot so limited.

Fuel is stored in a fuel storage reservoir 6 and is normally deliveredby way of a supply line 7 with the assistance of a pump 8 incorporatedtherein, to a tank 9 which may be a tank truck. In order that the fuelmay be rapidly pumped into the tank 9, the tank is provided with arelatively large vent 10 through which the fuel may be pumped and outthrough which the vapors may escape. It is the purpose of the vaporrecovery system S to recover those vapors which normally escape to theatmosphere and are lost from a financial standpoint, as well aspolluting the air.

In order that the vapors within the tank 9 may be prevented fromescaping, a suitable cover 11 is provided for the vent 10. If desired,the supply line 7 may be directly connected to the cover 11. A vent line12 extends from the cover 11 and leads to a compressor 13 forcompressing the recovered vapors. The vent line 12 has a check valve 14incorporated therein.

Basically speaking, incoming vapor is pumped by the compressor 13 intoan absorber 15 of an absorber system, which is generally identified bythe numeral 16. The incoming vapors are absorbed and condensed withinthe absorber 15 and returned in liquid form through a flash separator 19to the fuel storage reservoir 6.

AB SORBER SYSTEM The absorber system 16, of which the absorber 15 is apart, includes a tank 17 in which fuel 18 is maintained at asubstantially constant level by means of a float valve 20. The tank 17is provided with a drain 21. A vapor line 22 delivers vapor from thecompressor 13, in a manner to be described hereinafter, into the tank 17through a distribution manifold 23 which is submerged within the fuel18. The distribution manifold 23 is downwardly directed so as to preventfuel from entering distribution manifold 23 and to assure the passage ofthe vapor through the fuel 18. A baffle 24 is mounted within the fuel 18beneath the distribution manifold 23. A return line 25 is connected tothe lower portion of the tank 17 and has its free end disposed beneaththe baffle 24 for receiving the fuel 18.

The absorber system 16 also includes a fuel supply line 26 fordelivering fuel into the lower portion of the tank 17 from the fuelstorage reservoir 6. The end of the supply line 26 terminates above thedistribution manifold 23 and below the level of the fuel 18.

A fuel circulation line 27 is also connected to the lower portion of thetank 17 and has its pick up end disposed beneath the baffle 24. Fuelpassing into the fuel circulation line 27 is returned to the upperportion of the absorber through a return line 28 which is connected to adownwardly directed spray head which is mounted in a head space 29 inthe tank 17 above the fuel 18. The spray head 30 is downwardly directedfor directing sprayed liquid fuel against the upwardly rising vapor andair mixture within the head space 29.

Fuel flowing into the fuel recirculation line 27 is pumped by means of apump 31 partially through a bypass line 32 which leads directly to thereturn line 28, and passed partially through a refrigeration modulewhich is generally identified by the numeral 33. The refrigerationmodule 33 basically includes a compressor 34, a condenser 35 and anchiller 36. The usual expansion valve 37 is disposed between thecondenser and the chiller.

The condenser 35 is part of a liquid heat exchanger unit 38 whichutilizes the fuel stored within the fuel storage reservoir 6 as thecoolant. The heat exchanger unit 38 includes a jacket 40 surrounding thecondenser and fuel is pumped from the fuel storage reservoir 6 into thejacekt around the condenser coil 35 through a supply pipe 41 which isprovided with a pump 42. Fuel is returned from the jacekt 40 by means ofa return line 43 into the fuel storage reservoir 6.

That portion of the fuel 18 pumped by the pump 31 which does not passthrough the by-pass 32, as controlled by an orifice 44 in the by-pass32, is directed into a heat exchanger 45 of which the chiller 36 is apart, by means of a line 46. The line 46 leads into a jacket 47 of theheat exchanger 45 and fuel is circulated around the chiller coil 36. Thefuel 18, which has been cooled through its association with the chiller36, exits out of the jacket 47 through the return line 28.

The top of the tank 17 is also provided with bleed off line 48 throughwhich air and residual vapor escapes. The end result is that allincoming gas delivered into the absorber 15 through the line 22 eitheris bled off as air or becomes liquid and is returned to the fuel storagereservoir 6. Of course, it is impossible to completely separatehydrocarbon vapor from the air and a minute portion of the hydrocarbonvapor is bled off with the air through the bleed off line 48.

The lines 25 and 26 are connected to a heat exchanger 50. Fuel fromthefuel storage reservoir 6 is pumped through a supply pipe 51 by means ofa pump 52 into a coil 53 of the heat exchanger and then into the supplyline 26 to the tank 17. On the other hand, chilled fuel exiting from thetank 17 through line 25 passes into a casing 54 of the heat exchanger 50and circulates about the coil 53, reducing the temperature of the fuelpassing from the fuel storage reservoir 6 into the lower portion of thetank 17.

FLASH SEPARATOR The flash separator 19 basically includes a tank 55 inwhich fuel 18 is maintained in the lower portion thereof at a constantlevel. There is head space 56 above the fuel 18 and positioned withinthe head space 56 is a spray head 57 which is connected to a supply pipe58 for the flash separator 19. Flow through the supply pipe 58 iscontrolled by a valve 60 which is controlled by the float 20 so as tomaintain the desired fuel level within the tank 17.

A vapor return line 61 is connected to the upper portion of the tank 55while a fuel return line 62 leading to the fuel storage reservoir 6, isconnected to the lower portion of the tank 55. The level of fuel 18within the tank 55 is maintained by a float 63 controlling the positionof a valve 64 incorporated in the return line 62.

Although substantially all of the air within the absorber 15 is ventedto the atmosphere through bleed off line 48, the fuel passing outthrough the return line 25 still contains more absorbed air thandesired. When the fuel is sprayed into the flash separator 19, thisadditional absorbed air is released. This air together with fuel vaporpasses through the vapor return line 61 into the vapor line 12 with flowtherethrough being controlled by a pressure controlled valve 65. Thesubstantially air free fuel 18 passes into the fuel storage reservoirthrough the return line 62.

VAPOR FLOW SYSTEM Incoming vapor discharges from the compressor 13 intoa vapor line 66 and passes through a check valve 67 into a finned tubeaftercooler 68 which is of the air cooled type and which provides for amaterial lowering of the temperature of the compressed vapor.

The finned tube aftercooler 68 is connected to a liquid aftercooler 70which includes a heat exchange coil 71 disposed within a casing 72.Returning fuel passing from the heat exchanger 50 to the flash separator19 passes through a fuel line 69 into the upper end of the coil 71 anddischarges into the return line 58.

The compressed vapor circulates about the coil 71 and is cooled bycontact therewith. The cooled vapors pass out of the casing 72 into thevapor line 22 through which it passes into the absorber 15.

It is to be understood that the temperature of the compressed vaporpassing from the compressor 13 in many instances will be high enough tovaporize the fuel in the heat exchange coil 71 if the compressed vaporswere directly fed to the liquid heat exchanger 70. However, byconnecting the heat exchanger 70 in series with the finned tube heatexchanger 68, the compressed vapors are initially sufficiently cooled toprevent vaporization of the fuel passing through the coil 71. Inaddition to being able to maintain the fuel 18 as a liquid as it passesthrough the heat exchanger 70, the use of the finned tube aftercooleralso makes optimum use of the temperature gradients in the twoaftercoolers, thereby providing for greater over-all efficiency.

The vapor recovery system 5 also includes a vapor by-pass line 73connecting together the vapor lines 12 discharged within the head space29 through the spray I head 30. By refrigerating the recirculating fuel,the absorber 15 is operated at a lower temperature with the result thatit may also operate at a lower pressure with the same efficiency ofperformance. It has been found that the absorber operation is efficientwhen the temperature of the fuel 18 within the tank 17 is on the orderof 10F. to 40F. A typical installation would have the temperature of thefuel 18 at 0F.

The temperature of the fuel 18 within the absorber tank 17 is OF., therefrigerated fuel returning into the upper portion of the tank 17 willhave a temperature of -10F. and the pressure within the tank will be onthe order of 50 psig.

Under normal operating conditions, the temperature of fuel in the fuelstorage reservoir 6 will be 70F. and the temperature thereof will bereduced in the heat exchanger 50 to approximately 10F. On the otherhand, the temperature of the fuel 18 flowing through the heat exchanger50 will be increased to 45F. After the fuel passes through theaftercooled 70, it will have a temperature of 80F, at which temperatureit will be discharged into the flash separator 19 with the pressurewithin the flash separator 19 being on the order of 10 psig.

The incoming vapor passing from the compressor 13 into the aftercooler68 will have a temperature of 320F. while the compressed vapor passingfrom the aftercooler 68 into the aftercooler 70 will have a temperatureof 170F. The incoming vapor flowing into the absorber tank 17 will havea temperature of 80F.

It is to be noted that the pressure within the absorber tank 17eliminates the need for a pump to pump the returning fuel to the flashseparator 19. Also, the pressure within the flash separator providessufficient push to the liquid to effect the flow thereof to the fuelstorage reservoir 6.

Reference is now made to FIG. 3 wherein a slightly modified form ofvapor recovery system is illustrated, the modified vapor recovery systembeing generally identified by the numeral 75. The system 75 differs fromthe system 5 primarily in that in lieu of the fuel supply line 26directing fuel from the fuel storage reservoir 6 into the lower portionof the absorber tank 17, the recirculating fuel from the fuel storagereservoir is directed into the fuel circulation line 27 in advance ofthe pump 31. This permits the fuel being recirculated from the fuelstorage reservoir to be refrigerated before it is directed into theabsorber l5.

It is also to be noted that the system 75 has certain other omissions ascompared with respect to the system 5. While such omissions, and in someinstances modifications, are feasible and permissible, it is to beunderstood that the system 75 may be identical to the system 5 with theexception of the flow from the fuel storage reservoir into the absorber15.

Reference is now made to the modified compressor arrangement of FIG. 2.While the compressor 13 has only been schematically illustrated, it isto be understood that the compressor may be constructed to have amultiple stage so that it need not run at full capacity at all times.The compressor 13 may be formed as two compressors 76, 77 disposed inparallel and connected to a common vapor supply line 78, which could bethe vapor supply line 12.

The compressors 76 and 77 are commonly connected to the vapor line 66for directing compressed vapor into the aftercooler 68 and also theafter cooler 70, when the system is provided with both aftercoolers.

lt is to be understood that the compressors 76 and 77 may be run eitherindependently of one another or in unison with one antoher. It is alsoto be understood that each of the compressors 76,77 may be a multiplespeed compressor.

If desired, the vapor supply line may have coupled therein a saturator80 in advance of the by-pass line 73 and the compressor 13. Thesaturator may be of any construction, but normally would have directedinto the upper portion thereof a fuel supply line 81 for diwould also beconnected to the lower portion of the saturator a fuel return line 83which could deliver the fuel from the saturator either to the absorber15, the spray head 57 of the flash separator 19 or directed to the fuelstorage reservoir 6.

It is to be understood that the proportions of the components shown inthe drawings have been exaggerated for clarity purposes and that thevapor receovery systems are relatively compact, and if desired, could bemounted for mobility on a trialer or truck.

Although only three preferred embodiments of the invention have beenspecifically illustrated and described herein, it is to be understoodthat minor variations may be made in the vapor recovery systems withoutdeparting from the spirit and scope of the invention, as defined by theappended claims.

I claim:

1. A vapor recovery system including means for supplying volatile liquidto a tank, an absorber, means for delivering vapors from the tank to theabsorber, a supply of said liquid in the absorber for absorbing saidvapors therein, means for withdrawing liquid with absorbed vaporstherein from said absorber, refrigeration means for cooling the liquidin said absorber, and means for delivering said supply of said liquid insaid absorber from an external source other than said tank.

2. The system of claim 1 wherein said refrigeration means maintains thetemperature of said liquid in said absorber between 10F. and 40F.

3. The system of claim 1 wherein said refrigeration means maintains thetemperature of said liquid in said absorber on the order of 0F.

4. The system of claim 1 wherein said means connected to said absorberfor delivering said supply of liquid to said absorber from an externalsource is of the type for continuously delivering said supply of liquid.

5. The system of claim 1 wherein said refrigeration means is effectiveto cool said liquid in said absorber to a temperature below thetemperature of liquid in said external source, and heat exchange meansfor utilizing said withdrawn liquid as a coolant for said supply ofliquid being delivered from said external source to said absorber.

6. The system of claim 21 wherein said means for supplying volatileliquid to said tank is connected'to saidexternal source for receivingthe volatile liquid therefrom separate and apart from the means fordelivering liquid to said absorber.

7. The system of claim 1 in which said refrigeration means includesmeans for cooling at least a portion of said liquid withdrawn from saidabosrber and means for returning said cooled liquid to said absorberindependently of said external source.

8. The system of claim 7 in which said external source of volatileliquid is a reservoir, said refrigeration means includes a condenser,and means for supplying volatile liquid from said reservoir to saidcondenser as a coolant from said condensor and returning the same tosaid reservoir.

9. The system of claim 1 in which said external source of volatileliquid is a reservoir, said refrigeration means includes a condenser,and means for supplying volatile liquid from said reservoir to saidcondenser as a coolant for said condenser.

10. The system of claim 9 wherein said volatile liquid used as a coolantfor said condenser is returned to said reservoir.

11. A vapor recovery system including means for supplying volatileliquid to a tank, an absorber, means for delivering vapors from the tankto the absorber, a supply of said liquid in the absorber for absorbingsaid vapors therein, means for withdrawing liquid with absorbed vaporstherein from said absorber, and means for separating air and vaporscarried thereby from said withdrawn liquid.

12. A system according to claim 11 together with heat exchanger meansfor utilizing said withdrawn liquid as a coolant for vapors prior tobeing delivered to said absorber.

13. A system according to claim 11 together with means for returning theseparated air and vapors carried thereby to said absorber.

14. A system according to claim 13 together with means for deliveryingsaid liquid from which air has been removed to a reservoir.

15. A vapor recovery system including means for supplying volatileliquid to a tank, an absorber, means for delivering vapors from the tankto the absorber, a supply of said liquid in the absorber for absorbingsaid vapors therein, refrigeration means for cooling the liquid in saidabsorber, means for withdrawing liquid with absorbed vapors therein fromsaid absorber, means for delivering said supply ofliquid to saidabsorber from an external source other than said tank, and heatexchanger means for utilizing said withdrawn liquid as a coolant forsaid supply of liqud being delivered from said external source to saidabsorber.

16. The system of claim 15 wherein said refrigeration means maintainsthe temperature of said liquid in said absorber between F. and 40F.

17. The system of claim wherein said refrigeration means maintains thetemperature of said liquid in said absorber on the order of 0F.

18. The system of claim 15 together with means for separating alr fromsaid withdrawn liquid.

19. A system according to claim 15 together with additional heatexchanger means for also utilizing said withdrawn liquid as a coolantfor vapors being delivered to said absorber.

20. A system according to claim 19 wherein said additional heatexchanger means is downstream of said first heat exchanger means in thedirection of withdrawn liquid flow from said absorber.

21. A system according to claim 19 wherein there is a third heatexchanger means for receiving vapors and cooling the same in advance ofsaid second heat exchanger means. I

22. A vapor recovery system including means for supplying volatileliquid to a tank, an absorber, conduit means for receiving volatileliquid vapor from a tank being supplied with volatile liquid,multi-capacity compressor means connected between said conduit means andsaid absorber for receiving vapor from said conduit means and deliveringvapor to the absorber, said compressor means being of the type wherein apredetermined capacity may be selected in accordance with therequirements of the system, and further conduit means for removingcollected vapors from said absorber.

23. A system according to claim 22 wherein there is a pressurecontrolled by-pass associated with said compressor.

24. A system according to claim 22 wherein said multi-capacitycompressor is a multiple speed compressor.

25. A system according to claim 46 wherein said multi-capacitycompressor includes two separate selectively operable compressorsarranged in parallel.

26. A vapor recovery system including means for supplying volatileliquid to a tank, an absorber, means for delivering vapors from the tankto the absorber, a supply of said liquid in the absorber for absorbingsaid vapors therein, means for withdrawing liquid with absorbed vaporstherein from said absorber, and refrigeration means for cooling theliquid in said absorber, said refrigeration means including meansexternal of said absorber for cooling at least a portion of said liquidwithdrawn from said absorber and returning the cooled liquid to saidabsorber independently of said tank.

27. The system of claim 26 in which there are means for returninganother portion of said withdrawn liquid to said absorber independentlyof said refrigeration means.

28. The system of claim 27 wherein there are means for controlling thevolume of said another liquid portion returned to said absorberindependent of said refrigeration means.

1. A vapor recovery system including means for supplying volatile liquidto a tank, an absorber, means for delivering vapors from the tank to theabsorber, a supply of said liquid in the absorber for absorbing saidvapors therein, means for withdrawing liquid with absorbed vaporstherein from said absorber, refrigeration means for cooling the liquidin said absorber, and means for delivering said supply of said liquid insaid absorber from an external source other than said tank.
 2. Thesystem of claim 1 wherein said refrigeration means maintains thetemperature of said liquid in said absorber between 10*F. and -40*F. 3.The system of claim 1 wherein said refrigeration means maintains thetemperature of said liquid in said absorber on the order of 0*F.
 4. Thesystem of claim 1 wherein said means connected to said absorber fordelivering said supply of liquid tO said absorber from an externalsource is of the type for continuously delivering said supply of liquid.5. The system of claim 1 wherein said refrigeration means is effectiveto cool said liquid in said absorber to a temperature below thetemperature of liquid in said external source, and heat exchange meansfor utilizing said withdrawn liquid as a coolant for said supply ofliquid being delivered from said external source to said absorber. 6.The system of claim 21 wherein said means for supplying volatile liquidto said tank is connected to said external source for receiving thevolatile liquid therefrom separate and apart from the means fordelivering liquid to said absorber.
 7. The system of claim 1 in whichsaid refrigeration means includes means for cooling at least a portionof said liquid withdrawn from said abosrber and means for returning saidcooled liquid to said absorber independently of said external source. 8.The system of claim 7 in which said external source of volatile liquidis a reservoir, said refrigeration means includes a condenser, and meansfor supplying volatile liquid from said reservoir to said condenser as acoolant from said condensor and returning the same to said reservoir. 9.The system of claim 1 in which said external source of volatile liquidis a reservoir, said refrigeration means includes a condenser, and meansfor supplying volatile liquid from said reservoir to said condenser as acoolant for said condenser.
 10. The system of claim 9 wherein saidvolatile liquid used as a coolant for said condenser is returned to saidreservoir.
 11. A vapor recovery system including means for supplyingvolatile liquid to a tank, an absorber, means for delivering vapors fromthe tank to the absorber, a supply of said liquid in the absorber forabsorbing said vapors therein, means for withdrawing liquid withabsorbed vapors therein from said absorber, and means for separating airand vapors carried thereby from said withdrawn liquid.
 12. A systemaccording to claim 11 together with heat exchanger means for utilizingsaid withdrawn liquid as a coolant for vapors prior to being deliveredto said absorber.
 13. A system according to claim 11 together with meansfor returning the separated air and vapors carried thereby to saidabsorber.
 14. A system according to claim 13 together with means fordeliverying said liquid from which air has been removed to a reservoir.15. A vapor recovery system including means for supplying volatileliquid to a tank, an absorber, means for delivering vapors from the tankto the absorber, a supply of said liquid in the absorber for absorbingsaid vapors therein, refrigeration means for cooling the liquid in saidabsorber, means for withdrawing liquid with absorbed vapors therein fromsaid absorber, means for delivering said supply of liquid to saidabsorber from an external source other than said tank, and heatexchanger means for utilizing said withdrawn liquid as a coolant forsaid supply of liqud being delivered from said external source to saidabsorber.
 16. The system of claim 15 wherein said refrigeration meansmaintains the temperature of said liquid in said absorber between 10*F.and -40*F.
 17. The system of claim 15 wherein said refrigeration meansmaintains the temperature of said liquid in said absorber on the orderof 0*F.
 18. The system of claim 15 together with means for separatingaIr from said withdrawn liquid.
 19. A system according to claim 15together with additional heat exchanger means for also utilizing saidwithdrawn liquid as a coolant for vapors being delivered to saidabsorber.
 20. A system according to claim 19 wherein said additionalheat exchanger means is downstream of said first heat exchanger means inthe direction of withdrawn liquid flow from said absorber.
 21. A systemaccording to claim 19 wherein there is a third heat exchanger means forreceiving vapors and cooling the same in advance of said second heatexchanger means.
 22. A vapor recovery system including means forsupplying volatile liquid to a tank, an absorber, conduit means forreceiving volatile liquid vapor from a tank being supplied with volatileliquid, multi-capacity compressor means connected between said conduitmeans and said absorber for receiving vapor from said conduit means anddelivering vapor to the absorber, said compressor means being of thetype wherein a predetermined capacity may be selected in accordance withthe requirements of the system, and further conduit means for removingcollected vapors from said absorber.
 23. A system according to claim 22wherein there is a pressure controlled by-pass associated with saidcompressor.
 24. A system according to claim 22 wherein saidmulti-capacity compressor is a multiple speed compressor.
 25. A systemaccording to claim 46 wherein said multi-capacity compressor includestwo separate selectively operable compressors arranged in parallel. 26.A vapor recovery system including means for supplying volatile liquid toa tank, an absorber, means for delivering vapors from the tank to theabsorber, a supply of said liquid in the absorber for absorbing saidvapors therein, means for withdrawing liquid with absorbed vaporstherein from said absorber, and refrigeration means for cooling theliquid in said absorber, said refrigeration means including meansexternal of said absorber for cooling at least a portion of said liquidwithdrawn from said absorber and returning the cooled liquid to saidabsorber independently of said tank.
 27. The system of claim 26 in whichthere are means for returning another portion of said withdrawn liquidto said absorber independently of said refrigeration means.
 28. Thesystem of claim 27 wherein there are means for controlling the volume ofsaid another liquid portion returned to said absorber independent ofsaid refrigeration means.